1. Field of Invention
The present invention relates to a digital broadcasting system, and particularly to a method of transmitting and receiving digital broadcasts and digital data broadcasts suitable for mobile terminals driven by batteries and a transmission apparatus and a reception apparatus in the digital broadcasting system.
2. Description of the Related Art
In Europe, digital terrestrial broadcasts are transmitted to stationary receiving terminals according to the standard (DVB-T EN 300 477) developed by the European Technical Standards Institute (ETSI). In order to receive a digital terrestrial broadcast at a mobile terminal, a broadcast wave is divided into frequency segments in advance and then transmitted, as defined in a Japanese domestic standard (ARIB STD-B31). In this case, a popular television receiver receives all the segments to reproduce them on a large-sized screen, while a mobile terminal receives only one or a few segments to reproduce them on a small-sized screen.
Unlike the Japanese standard, the European standard does not define this partial reception of the frequency segments, so it is necessary to receive all the frequency bands of the broadcast wave in series in order to receive the broadcast service at the mobile terminal, which results in the consumption of much power particularly in the high frequency front end module. Therefore, in a mobile terminal driven by a battery, the battery is drained so quickly that it becomes difficult for the terminal to receive a long-time broadcast service continuously. This is a practical problem.
Against this backdrop, a scheme has been suggested, in which as shown in FIG. 1, a digital broadcast stream including services A to D as data bursts is transmitted in a short time by performing time-division multiplexing of these service data exclusively on each service, and the power is supplied to the high frequency front end module of the receiver only during the periods of arrival of the data bursts of the target service (namely, the high frequency front end module is powered off during the periods of arrival of the data bursts of the other services) (See European Laid-open Patent Application No. 1337071). This scheme enables reduction of average power consumption employing the characteristic that the duration of the arrival of the data bursts of the target service selected by the user is sufficiently shorter than the duration of the arrival of the data bursts of the other services. This scheme is referred to as “time-slicing”.
However, the above time-slicing scheme has the following problems. Once the receiver misses a data burst in the condition of a low carrier/noise ratio (hereinafter referred to as “C/N”) due to a bad radio wave reception, it cannot obtain the data burst normally until the recovery of synchronization, and therefore the reproduction of the service is interrupted. In addition, since the tuning/demodulation unit needs to be powered on continuously for the recovery of synchronization, much power is consumed.